This is a custom sized filter. As a result, these filters may not be returned for refund or credit. All custom size air filters are built to tolerances of + or - 1/8. This custom sized filter will ship within 2 business days. - MERV 8 Rating - Electrostatic charge captures airborne allergens SMALLER THAN 1 micron including fine dust, smoke, dander, mold, pet dander and dust mites. - Also traps most large allergens including pollen and lint. - Up to 20-times more effective at capturing micro particles than ordinary fiberglass filters. Designed for uniform air flow. - Lasts UP TO 3 months. - Will not support the growth of bacteria, mold, mildew or fungi in normal use. - This product is listed and rated by Underwriters Laboratories as U.L. Class 2.